Metrology of Psiloquest's Application Specific Pads (ASP) for CMP Applications

There is a need to develop a metrology metrics for evaluation of pad CMP performance before putting them in to service. This has been attempted on Psiloquest's application specific pads (ASP) in which the pad surface is tuned to match the mechanical properties of the target substrate. The ASP is made up of thermoplastic foams co extruded with condensed polyolefin. The chemical and mechanical properties of the pad-wafer interface are tuned by coating the pad with ceramic thin films by surface coating method such as chemical vapor deposition (CVD). The surface of the pad is characterized using metrology techniques such as ultra sound reflectivity, XPS and nanoindentation. The cross section of the pads was characterized using SEM. The mechanical properties of bulk pad materials were studied using Dynamic Mechanical Analysis (DMA). A test was performed on the pads to measure the static coefficient of friction (COF) and wear rate. The pads were polished using CETR CP-4 bench top CMP tester to evaluate the dynamic COF, Acoustic Emission (AE) signal and removal rate during a simulated Tungsten CMP process. The thickness of the ceramic coating on the surface of the ASP played an important role in determining these tribological properties. The results of the various static and dynamic tests performed on the pad were cross tabulated to evaluate their correlation.